Clear glass composition

ABSTRACT

Glass is provided so as to have high visible transmission and/or fairly clear or neutral color. In certain example embodiments of making glass according to examples of the invention, the glass batch may include a base glass (e.g., soda lime silica base glass) and, in addition, by weight percentage: 
                                       total iron (expressed as Fe 2 O 3 ):    0.01 to 0.30%         erbium oxide (e.g., Er 2 O 3 ):    0.01 to 0.30%         cerium oxide (e.g., CeO 2 ):   0.005 to 0.30%.                                 
Optionally, neodymium oxide (e.g., Nd 2 O 3 ) may also be provided in the glass in certain example embodiments. In other embodiments, the cerium oxide may be replaced with or supplemented by NaNO 3  or some other nitrate(s) as an oxidizer.

This application is a Divisional of application Ser. No. 10/056,051,filed Jan. 28, 2002 now U.S. Pat. No. 6,610,622, the entire content ofwhich is incorporated herein by reference in this application.

BACKGROUND OF THE INVENTION

This invention relates to glass compositions and methods of making thesame. More particularly, this invention relates to glass having highlight transmittance in the visible range and/or fairly neutral color.Such glass compositions are thus useful, for example, in architecturalwindows, patterned glass applications, solar cells, and/or automotivewindows.

Glass that is fairly clear in color and highly transmissive to visiblelight (e.g., at least 75% transmissive, or even more preferably at least80% transmissive) is sometimes desirable. One way of achieving such asglass is to use very pure base glass materials (e.g., substantially freeof colorants such as iron). However, base materials with a high degreeof purity are expensive and thus not always desirable and/or convenient.In other words, for example, the removal of iron from glass rawmaterials has certain practical and/or economical limits.

As can be appreciated from the above, glass raw materials (e.g., silica,soda ash, dolomite, and/or limestone) typically include certainimpurities such as iron. The total amount of iron present is expressedherein in terms of Fe₂O₃ in accordance with standard practice. However,typically, not all iron is in the from of Fe₂O₃. Instead, iron isusually present in both the ferrous state (Fe²⁺; expressed herein asFeO, even though all ferrous state iron in the glass may not be in theform of FeO) and the ferric state (Fe³⁺). Iron in the ferrous state(Fe²⁺; FeO) is a blue-green colorant, while iron in the ferric state(Fe³⁺) is a yellow-green colorant. The blue-green colorant of ferrousiron (Fe²⁺; FeO) is of particular concern when seeking to achieve afairly clear or neutral colored glass, since as a strong colorant itintroduces significant color into the glass. While iron in the ferricstate (Fe³⁺) is also a colorant, it is of less concern when seeking toachieve a glass fairly clear in color since iron in the ferric statetends to be weaker as a colorant than its ferrous state counterpart.

In view of the above, it is apparent that there exists a need in the artfor a new glass composition which enables a glass to have fairly clearcolor and/or high visible transmission, without having to resort toextremely pure (i.e., free of iron) glass raw materials.

SUMMARY OF THE INVENTION

An object of this invention is to provide a glass that has fairly clearcolor and/or high visible transmission.

Another object of this invention is to provide a glass having a visibletransmission of at least 75% (more preferably at least 80%, and mostpreferably at least 85%), wherein in making the glass a batch thereforincludes a base glass (e.g., soda lime silica glass) and in additioncomprising (or consisting essentially of in certain embodiments), byweight percentage:

total iron (expressed as Fe₂O₃):  0.01 to 0.30% erbium oxide (e.g.,Er₂O₃):  0.01 to 0.30% cerium oxide (e.g., CeO_(2):) 0.005 to 0.30%.Optionally, other colorants such as neodymium oxide (e.g., Nd₂O₃) mayalso be provided in certain example embodiments. While cerium oxide ispreferred in many embodiments, its presence is not a requirement. Inother embodiments of this invention, the cerium oxide (e.g., CeO₂) inthe glass batch may be either replaced or supplemented by sodium nitrate(NaNO₃) as an oxidizer.

Another object of this invention is to fulfill one or more of theabove-listed objects and/or needs.

Certain example embodiments of the invention fulfill one or more of theabove-listed objects and/or needs by providing a method of making glass,the method comprising:

providing a glass batch comprising: Ingredient wt. % SiO₂ 67-75% Na₂O10-20% CaO  5-15% MgO  0-5% Al₂O₃  0-5% K₂O  0-5% total iron (expressedas Fe₂O₃)  0.01 to 0.30% erbium oxide  0.01 to 0.30% cerium oxide and/ora nitrate 0.005 to 2.0% neodymium oxide    0 to 0.15%melting the batch and forming a resulting glass that has visibletransmission of at least 75%, a transmissive a* color value of −1.0 to+1.0, and a transmissive b* color value of −1.0 to +1.5.

Certain other example embodiments of this invention fulfill one or moreof the above-listed objects and/or needs by providing a glasscomprising:

total iron (expressed as Fe₂O₃)  0.01 to 0.30% erbium oxide  0.01 to0.30% cerium oxide 0.005 to 0.30%.

Certain other example embodiments of this invention fulfill one or moreof the above-listed objects and/or needs by providing a method of makingglass, the method comprising providing a glass batch comprising:

total iron (expressed as Fe₂O₃):  0.01 to 0.30% erbium oxide:  0.01 to0.30% cerium oxide and/or a nitrate: 0.005 to 2.0%, and using the glassbatch to make glass.

Certain other example embodiment of this invention fulfill one or moreof the above-listed objects and/or needs by providing a glasscomprising:

total iron (expressed as Fe₂O₃) 0.01 to 0.30%, and erbium oxide 0.01 to0.30%.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION

Glasses according to different embodiments of this invention may beused, for example, in the automotive industry (e.g., windshields,backlites, side windows, etc.), in architectural applications, forpatterned glass applications, solar cell applications, and/or in othersuitable applications.

Certain glasses according to this invention utilize soda-lime-silicaflat glass as their base composition/glass. In addition to basecomposition/glass, a unique colorant portion is provided in order toachieve a glass that is fairly clear in color and/or has a high visibletransmission. An exemplary soda-lime-silica base glass according tocertain embodiments of this invention, on a weight percentage basis,includes the following basic ingredients:

TABLE 1 EXAMPLE BASE GLASS Ingredient Wt. % SiO₂ 67-75% Na₂O 10-20% CaO 5-15% MgO  0-5% Al₂O₃  0-5% K₂O  0-5% BaO  0-1%Other minor ingredients, including various conventional refining aids,such as SO₃, carbon, and the like may also be included in the baseglass. In certain embodiments, for example, glass herein may be madefrom batch raw materials silica sand, soda ash, dolomite, limestone,with the use of salt cake (SO₃) and/or Epsom salts (e.g., about a 1:1combination of both) as refining agents. Preferably, soda-lime-silicabased glasses herein include by weight from about 10-15% Na₂O and fromabout 6-12% CaO. While a soda-lime-silica base glass set forth above ispreferred in certain embodiments of this invention, this invention isnot so limited. Thus, other base glasses (e.g., borosilicate glass) mayinstead be employed in alternative embodiments of this invention.

In addition to the base glass (e.g., see Table 1 above), in making glassaccording to the instant invention the glass batch includes materials(including colorants and/or oxidizers) which cause the resulting glassto be fairly neutral in color and/or have a high visible lighttransmission. These materials may either be present in the raw materials(e.g., small amounts of iron), or may be added to the base glassmaterials in the batch (e.g., cerium, erbium, etc.). In certainpreferred embodiments, the resulting glass has visible transmission ofat least 75%, more preferably at least 80%, and most preferably at least85%.

In certain embodiments of this invention, in addition to the base glass,the glass batch includes materials as set forth in Table 2 below (interms of weight percentage of the total glass composition):

TABLE 2 EXAMPLE GLASS BATCH OF FIRST EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed  0.01-0.30%0.02-0.20% 0.03-0.15% as Fe₂O₃): erbium oxide (e.g., Er₂O₃):  0.01-0.30%0.02-0.20% 0.03-0.13% cerium oxide (e.g., CeO₂): 0.005-0.30% 0.01-0.18%0.03-0.12%

The batch is melted and glass formed using the known float process.Optionally, in certain example embodiments of the invention, neodymiumoxide (e.g., Nd₂O₃) may be added to the batch, as exemplified below inTable 3 according to a second example embodiment of this invention (thematerial listed in Table 3 are in addition to the base glass describedabove).

TABLE 3 EXAMPLE GLASS BATCH OF SECOND EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed as 0.01-0.30%  0.02-0.20%  0.03-0.15% Fe₂O₃): erbium oxide  0.01-0.30% 0.02-0.20%  0.03-0.13% (e.g., Er₂O₃): cerium oxide 0.005-0.30% 0.01-0.18%  0.03-0.12% (e.g., CeO₂): neodymium oxide 0.005-0.15%0.010-0.050% 0.010-0.030% (e.g., Nd₂O₃):

In certain embodiments of this invention (e.g., first and/or secondembodiments above), the colorant portion is substantially free of othercolorants (other than potentially trace amounts). However, it should beappreciated that amounts of other materials (e.g., refining aids,melting aids, colorants and/or impurities) may be present in the glassin certain other embodiments of this invention without taking away fromthe purpose(s) and/or goal(s) of the instant invention. It is noted thatwhile the presence of cerium oxide is preferred in many embodiments ofthis invention, it is not required in all embodiments. Moreover, it ispossible to use little or no Er in certain embodiments of thisinvention.

In other embodiments of this invention, the cerium oxide (e.g., CeO₂)may be either replaced or supplemented by NaNO₃ in the glass batch; seethe third, fourth and fifth embodiments below (the batch materials inTables 4-6 below are in addition to the base class raw materialsdescribed above).

TABLE 4 EXAMPLE GLASS BATCH OF THIRD EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed as0.01-0.30% 0.02-0.20% 0.03-0.15% Fe₂O₃): erbium oxide (e.g., Er₂O₃):0.01-0.30% 0.02-0.20% 0.03-0.13% sodium nitrate (NaNO₃):  0.1-2.0% 0.2-1.5%  0.3-1.2%

TABLE 5 EXAMPLE GLASS BATCH OF FOURTH EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed as 0.01-0.30%  0.02-0.20%  0.03-0.15% Fe₂O₃): erbium oxide  0.01-0.30% 0.02-0.20%  0.03-0.13% (e.g., Er₂O₃): sodium nitrate  0.1-2.0% 0.2-1.5%  0.3-1.2% (NaNO₃): neodymium oxide 0.005-0.15% 0.010-0.050%0.010-0.030% (e.g., Nd₂O₃):

TABLE 6 EXAMPLE GLASS BATCH OF FIFTH EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed as0.01-0.30% 0.02-0.20% 0.03-0.15% Fe₂O₃): erbium oxide (e.g., Er₂O₃):0.01-0.30% 0.02-0.20% 0.03-0.13% cerium oxide (e.g., CeO₂):   0-0.30%  0-0.18%   0-0.12% sodium nitrate (NaNO₃):   0-2.0%  0.2-1.5%  0.3-1.2%

In the fifth embodiment (see Table 6 above), cerium oxide (e.g., CeO₂)and sodium nitrate (NaNO₃) may be combined as oxidizers, so as to causethe effects of equations (1) and (2) below. Accordingly, one or both ofcerium oxide and/or sodium nitrate may be provided in this fifthembodiment.

It is noted that in certain embodiments herein, the amount of total ironmay even be less than 0.10%.

The above batches are melted and the float process used to form glass(e.g., soda lime silica glass) in a known manner.

The total amount of iron present in the glass batch and in the resultingglass, i.e., in the colorant portion thereof, is expressed herein interms of Fe₂O₃ in accordance with standard practice. This, however, doesnot imply that all iron is actually in the form of Fe₂O₃ (see discussionabove in this regard). Likewise, the amount of iron in the ferrous state(Fe⁺²) is reported herein as FeO, even though all ferrous state iron inthe glass batch or glass may not be in the form of FeO. As mentionedabove, iron in the ferrous state (Fe²⁺; FeO) is a blue-green colorant,while iron in the ferric state (Fe³⁺) is a yellow-green colorant; andthe blue-green colorant of ferrous iron is of particular concern, sinceas a strong colorant it introduces significant color into the glasswhich can sometimes be undesirable when seeking to achieve a neutral orclear color.

According to certain example embodiments of this invention, the presenceof cerium oxide (e.g., CeO₂) as an oxidizer in the glass batch acts as achemical decolorizer since during melting of the glass batch it causesiron in the ferrous state (Fe²⁺; FeO) to oxidize to the ferric state(Fe³⁺) as illustrated by the following equation:Fe²⁺+Ce⁴⁺=Fe³⁺+Ce³⁺  (1)

Equation (1) shows that the presence of cerium oxide in the glass batchcauses an amount of the strong blue-green colorant of ferrous iron(Fe²⁺; FeO) to oxidize into the weaker yellow-green ferric iron colorant(Fe³⁺) during the glass melt (note: some ferrous state iron will usuallyremain in the resulting glass, as potentially may some Ce⁴⁺).Accordingly, a significant portion of the CeO₂ added to the originalglass batch prior to the melt is transformed during the melt into Ce₂O₃which is present in the resulting glass. The aforesaid oxidation of theiron tends to reduce coloration of the glass, and does not significantlydecrease visible light transmission of the resulting glass (in certaininstances, this may even causes visible transmission to increase).However, those of skill in the art will appreciate that there stillexists significant coloration in the glass due to the ferric iron ifonly the iron and cerium oxide are provided. In other words, it has beenfound that adding cerium oxide to only iron containing glass is notsufficient to achieve a desired fairly clear or neutral color.

It is noted that, like Fe₂O₃, the phrase “cerium oxide” as used hereinrefers to total cerium oxide (i.e., including cerium oxide in both theCe⁴⁺ and Ce³⁺ states).

As mentioned above, the cerium oxide may be replaced by, or supplementedwith, sodium nitrate in certain example embodiments of this invention.In embodiments where sodium nitrate (NaNO₃) is provided in the glass(e.g., see Tables 3-5 above), it functions in a manner similar to ceriumoxide as shown in the below equation (but note the potential for oxygenbubbles). In particular, like cerium oxide, sodium nitrate can be addedto the glass batch as an oxidizer to cause an amount of the strongblue-green colorant of ferrous iron (Fe²⁺; FeO) to oxidize into theweaker yellow-green ferric iron colorant (Fe³⁺) during the glass melt(note: some ferrous state iron will usually remain in the resultingglass):Fe²⁺NO₃=Fe³⁺+NO₂+½O₂   (2)

Those skilled in the art will recognize that the most of the nitrate(e.g., sodium nitrate) added to the glass batch decomposes during themelt so that some burns off as NO_(x) while other parts of it end up inthe glass as Na₂O. While sodium nitrate (NaNO₃) is utilized as anoxidizer in Tables 4-6 above, the instant invention is not so limited.For example, other nitrates (e.g., potassium nitrate KNO₃, or any othersuitable nitrate) may be used instead of or in addition to sodiumnitrate in alternative embodiments of this invention.

In order to compensate for the color caused by the ferric iron resultingfrom the addition of the cerium oxide and/or sodium nitrate, it has beenfound that adding erbium oxide (e.g., Er₂O₃ or any other suitablestoichiometric form) and/or neodymium oxide (e.g., Nd₂O₃ of any othersuitable stoichiometric form) causes the color of the resulting glass tobecome more clear (i.e., more neutral as the a* and/or b* color value(s)move(s) toward neutral 0). Erbium oxide acts as a pink colorant, whileneodymium oxide acts as a purple colorant. One or both of Er and/or Ndapparently acts to physically compensate for the iron color, therebymaking the color of the glass more neutral which is desirable in certainembodiments of this invention, while enabling the glass to still havehigh visible transmission.

It will be appreciated by those skilled in the art that the addition ofcerium oxide and/or sodium nitrate (see equations (1) and (2) above)results in a glass with a lower “redox” value (i.e., less iron in theferrous state FeO). In this regard, the proportion of the total iron inthe ferrous state (FeO) is used to determine the redox state of theglass, and redox is expressed as the ratio FeO/Fe₂O₃, which is theweight percentage (%) of iron in the ferrous state (FeO) divided by theweight percentage (%) of total iron (expressed as Fe₂O₃) in theresulting glass. Due to the presence of the cerium oxide and/or sodiumnitrate, the redox of glass according to certain example embodiments ofthis invention is rather low; in particular, glass according to certainexample embodiments of this invention may have a redox value (i.e.,FeO/Fe₂O₃) of less than or equal to 0.25, more preferably less than orequal to 0.20; even more preferably less than or equal to 0.15, and mostpreferably less than or equal to 0.13. Moreover, resulting glassaccording to certain example embodiments of this invention may includeiron in the ferrous state (FeO) in an amount (wt. %) of less than orequal to 0.020%, more preferably less than or equal to 0.015%, and mostpreferably less than or equal to 0.011%.

It is noted that glass according to this invention is often made via theknown float process in which a tin bath is utilized. It will thus beappreciated by those skilled in the art that as a result of forming theglass on molten tin in certain exemplary embodiments, small amounts oftin or tin oxide may migrate into surface areas of the glass on the sidethat was in contact with the tin bath during manufacture (i.e.,typically, float glass may have a tin oxide concentration of 0.05% ormore (wt.) in the first few microns below the surface that was incontact with the tin bath).

In view of the above, glasses according to certain example embodimentsof this invention achieve a neutral or substantially clear color and/orhigh visible transmission. In certain embodiments, resulting glassesaccording to certain example embodiments of this invention may becharacterized by one or more of the following transmissive optical orcolor characteristics when measured at a thickness of from about 1 mm-6mm (most preferably a thickness of about 0.219 inches; this is anon-limiting thickness used for purposes of reference only) (Lta isvisible transmission %):

TABLE 7 CHARACTERISTICS OF CERTAIN EXAMPLE EMBODIMENTS CharacteristicGeneral More Preferred Most Preferred Lta (Ill. C, 2 deg.):   >=75%  >=80%   >=85% % UV (Ill. C. 2 deg.):   <=85%   <=80%   <=75% % TS(Ill. C. 2 deg.):   <=90%   <=87%   <=85% % FeO (wt. %): <=0.020%<=0.015% <=0.011% L* (Ill. D65, 10 deg.): 90-100 n/a n/a a* (Ill. D65,10 deg.): −1.0 to +1.0 −0.60 to +0.60 −0.30 to +0.50 b* (Ill. D65, 10deg.): −1.0 to +1.5 −0.70 to +1.0 −0.30 to +0.40

As can be seen from Table 7 above, glasses of certain embodiments ofthis invention achieve desired features of fairly clear color and/orhigh visible transmission, while not requiring iron to be eliminatedfrom the glass composition. This may be achieved through the provisionof the unique material combinations described herein.

EXAMPLES

Example glasses of this invention may be made from batch ingredientsusing well known glass melting and refining techniques. The followingapproximate base glass batch was used for the Examples herein (note: thebelow-listed ingredients in the batch will add up to 100% by weight onceoxides thereof are accounted for; thus, they need not add up to onehundred as raw materials):

Batch Ingredient for Base Glass Parts by Wt. sand 71.5 soda ash 23.7dolomite 18.32 limestone 6.1 Epsom salt 0.9

In addition to the base glass batch materials above, the materials setforth below were present in the original batch(es) for the Examples(compound amounts given in wt. %). It is noted that Examples 1-8 areaccording to different example embodiments of this invention, while CA,CB and CC are Comparative Examples provided for purposes of comparisonwith Examples 1-8. In particular, Comparative Example A (CA) should becompared to Examples 1-3 of this invention since they all have the sameamount of total iron, while Comparative Example B (CB) should becompared to Examples 4-5 of this invention since they all have the sametotal iron amount, and Comparative Example C (CC) should be compared toExamples 6-8 of this invention since they all have the same amount oftotal iron.

BATCH MATERIALS IN EXAMPLES 1-8 (IN ADDITION TO BASE BATCH) Compound CAEx. 1 Ex. 2 Ex. 3 CB Ex. 4 Ex. 5 CC Ex. 6 Ex. 7 Ex. 8 Fe₂O_(3:) 0.1020.102 0.102 0.102 0.09 0.09 0.09 0.033 0.033 0.033 0.033 Er₂O_(3:) 00.06 0.08 0.11 0 0.086 0.08 0 0 0.10 0.09 CeO_(2:) 0 0.035 0.035 0.035 00.066 0.06 0 0.08 0.10 0.09 Nd₂O_(3:) 0 0 0 0 0 0 0 0.02 0.02 0.03 0.025

The batches were melted and glass formed using known techniques. Solarcharacteristics for the resulting Example glasses were as follows in thetable below, with the below measurements taken after the melt andformation of the glass. It is noted that Lta (visible transmission %),UV transmission %, and % TS were measured using Ill. C, 2 degreeobserver, while transmissive L*, a* and b* color coordinates (CIE) weremeasured using Ill. D65, 10 degree observer. Moreover, Dom. λ stands fordominant wavelength, and Pe stands for excitation purity. All glasssamples were about 0.219 inches thick (about 5.5-5.6 mm thick).

CHARACTERISTICS OF EXAMPLES 1-8 GLASSES Character- istic CA Ex. 1 Ex. 2Ex. 3 CB Ex. 4 Ex. 5 CC Ex. 6 Ex. 7 Ex. 8 % Lta 88.4 88.0 87.7 86.2 88.889.7 89.4 88.0 89.6 89.0 88.5 % UV 74.5 68.9 74.8 73.6 76.9 65.9 66.476.2 65.9 63.2 63.6 % TS 79.6 83.1 81.3 79.8 79.2 84.5 84.0 79.5 84.986.0 84.9 FeO (wt. %) .0232 .011 .0177 .0191 .0254 .009 .0104 .023 .0079.0042 .0065 Dom. λ (nm) 498 562 487 487 493 573 564 492 537 566 581 Pe %0.64 0.37 0.24 0.22 0.9 0.48 0.27 0.96 0.25 0.07 0.07 L* 95.5 95.2 95.194.4 95.7 95.8 95.7 93.6 95.9 95.6 95.4 a* −1.54 −0.34 −0.18 −0.15 −1.49−0.1 −0.21 −1.41 −0.72 0.09 −0.05 b* 0.24 0.51 −0.12 −0.11 −0.15 0.580.39 −0.29 0.47 0.11 0.14

It can be seen from the above that glasses according to differentembodiments of this invention (Examples 1-8) have one or more of thefollowing example advantages over the Comparative Examples (CA, CB, andCC): (i) glasses according to Examples 1-8 had more neutral color thanthe respective Comparative Examples CA, CB and CC (it is noted that theComparative Examples did not include erbium or cerium); (ii) glassesaccording to Examples 1-8 had less FeO (i.e., less iron in the ferrousstate) than the respective examples (CA, CB and CC), even though therespective Examples and Comparative Examples for comparing therewith hadthe same amount of total iron; and/or (iii) glasses according toExamples 1-8 had lower excitation purity (Pe) than the respectiveComparative Examples CA, CB and CC. High visible transmission (Lta) wasmaintained in Examples 1-8.

With respect to color, it can be seen for example that Example 1 wascharacterized by much more neutral a* color than CA (i.e., a* was closerto zero in Example 1 than in CA); compare a*=−0.34 of Example 1 witha*=−1.54 of Comparative Example A (CA). In a similar manner, it can beseen for example that Example 4 had much more neutral a* color than CB(i.e., a* was closer to zero in Example 4 than in CB); compare a*=−0.1of Example 4 with a*=−1.49 of Comparative Example B (CB). In a similarmanner, it can be seen for example that Example 7 had much more neutrala* color than CC (i.e., a* closer to zero in Example 7 than in CC);compare a*=0.09 of Example 7 with a*=−1.41 of Comparative Example C(CC). The improved neutral color of example embodiments of thisinvention is a result of the unique material combinations used inglasses according to example embodiments of this invention.

It is noted that in any of Examples 1-8 above, the cerium oxide may bereplaced with sodium nitrate in certain embodiments of this invention(see amounts in Tables 4-6 above). Certain examples according to otherembodiments of this invention are set forth below (same base glass asabove for other examples), where Examples 10-11 utilize sodium nitratewas used instead of or in addition to cerium oxide. It is noted thatExamples 9-11 differed from Examples 1-8 above in that for Examples 9-11each glass sample was only 0.161 inches thick.

BATCH MATERIALS IN EXAMPLES 9-11 (IN ADDITION TO BASE BATCH) CompoundEx. 9 Ex. 10 Ex. 11 Fe₂O_(3:) 0.054 0.055 0.048 Er₂O_(3:) 0.06 0 0CeO_(2:) 0.06 0.09 0 NaNO_(3:) 0 0.5 0.78 Nd₂O_(3:) 0 0 0

The above batches were melted and glass formed using known techniques.Solar characteristics for the resulting Example glasses were as followsin the table below, with the below measurements taken after the melt andformation of the glass.

CHARACTERISTICS OF EXAMPLES 9-11 GLASSES Characteristic Ex. 9 Ex. 10 Ex.11 % Lta 90.43 91.32 90.75 % UV 71.81 72.63 77.73 % TS 87.78 90.54 88.14FeO (wt. %) 0.0031 0.0007 0.0048 Dom. λ(nm) 578 570 566 Pe % 0.63 0.410.53 L* 96.11 96.52 96.29 a* 0.09 −0.18 −0.36 b* 0.67 0.5 0.67

As with the previous examples, it can be seen that Examples 9-11 haveimproved color (more neutral) and high visible transmission relative tothe comparative examples, albeit reduced thickness. It is noted thatExamples 9-11 utilized a smaller amount of total iron than Examples 1-8.Examples 9-11 illustrate that according to certain example embodimentsof this invention, the glass may even have a visible transmission of atleast 90% when at a reference thickness of about 0.161 inches.

The terms, and characteristics, of ultraviolet light transmittance (%UV), dominant wavelength, and excitation purity (i.e. % “purity”, or Pe)are well understood terms in the art, as are their measurementtechniques. Such terms are used herein, in accordance with their wellknown meaning, e.g., see U.S. Pat. No. 5,308,805. In particular,ultraviolet transmittance (% UV) is measured herein using Parry Moon AirMass=2 (300-400 nm inclusive, integrated using Simpson's Rule at 10 nmintervals). Dominant wavelength (DW) is calculated and measuredconventionally in accord with the aforesaid CIE Publication 15.2 (1986)and ASTM: E 308-90. The term “dominant wavelength” includes both theactual measured wavelength and, where applicable, its calculatedcomplement. Excitation purity (Pe or % “purity”) is measuredconventionally in accordance with CIE Publication 15.2 (1986) and ASTM:E 308-90.

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such features,modifications and improvements are therefore considered to be a part ofthis invention, the scope of which is to be determined by the followingclaims:

1. Glass comprising: a base glass portion comprising: Ingredient wt. %SiO₂ 67-75% Na₂O 10-20% CaO  5-15%

a colorant portion comprising: total iron (expressed as Fe₂O₃) 0.054 to0.30% erbium oxide  0.01 to 0.30% cerium oxide  0.01 to 0.18%

wherein the glass has visible transmission of at least 80%, atransmissive a* color value of −1.0 to +1.0, and a transmissive b* colorvalue of −1.0 to +1.5.
 2. The glass of claim 1, wherein the glass has aredox value (FeO/Fe₂O₃) of less than or equal to 0.20.
 3. The glass ofclaim 1, wherein the glass has a redox value (FeO/Fe₂O₃) of less than orequal to 0.15.
 4. The glass of claim 1, wherein the glass has a redoxvalue (FeO/Fe₂O₃) of less than or equal to 0.13.
 5. The glass of claim1, wherein the glass comprises from 0.02 to 0.20% erbium oxide.
 6. Theglass of claim 5, wherein the glass comprises from 0.03 to 0.13% erbiumoxide.
 7. The glass of claim 1, wherein the glass has a visibletransmission of at least 85%.
 8. The glass of claim 1, wherein the glasshas a visible transmission of at least 90%.
 9. The glass of claim 1,wherein the glass comprises less than or equal to 0.020% FeO.
 10. Theglass of claim 1, wherein the glass comprises less than or equal to0.011% FeO.
 11. The glass of claim 1, wherein the glass comprises fromabout 10-15% Na₂O and from about 6-12% CaO.